Acrolein-formaldehyde condensation products and process of applying the same to cellulose fabric



United States Patent '0 ACROLEIN-FORMALDEHYDE CONDENSATION PRODUCTS ANDPROCESS OF APPLYING THE SAME T CELLULOSE FABRIC Dmitry M. Gagarine andHenry Repokis, Danville, Va.,

.assignors to Dan River Mills, Incorporated, a corporation of VirginiaNo Drawing. Application May 3, 1952,

Serial No. 286,038

11 Claims. (Cl. 8116.4)

goods. These treated materials also possess the desirable properties ofpermanent dimensional stability and freedom from yellowing anddiscoloration regardless of sub sequent treatments.

Although certain compounds heretofore known and used for treatingtextiles will provide the desired wrinkleresistant characteristics, theyare deficient with respect to resistance to commercial launderingconditions and to chlorine retention. -Agood example of suchua compoundis the melamine-formaldehyde-urea reaction .disclosed in our applicationSerial No. 187,854, filed 10ctober 2, 1950. That product imparts totextile ma-terials such as cotton, rayons, etc., excellentcrease-resistant or wrinkle-resistant characteristics that have longbeen desired, but are not obtainable with the prior art products andprocesses, and cloth treated with compounds disclosed in thatapplication has been satisfactorily produced and sold on a widecommercial scale. The process is applied principally to fine .gingham orother sheer cotton goods and rayons for use in making ladies andchildrens dresses. Such products are normally laundered "at home withoutthe use of strong bleaches or highly alkaline soaps and/therefore donot'involve the problems arising from commercial laundering conditions.

However, it is equally desirable to provide wrinkle or crease-resistantcharacteristics to goods and garments that are commonly laundered incommercial laundries, such as, for example, sheets, pillow cases, mens.shirts and table linens. It has heretofore been a major commer-cialproblem to produce these textile products and garments with the desiredcrease-resistance .and, concomitantly, resistance to commerciallaundering conditions. The process and product of the present inventionhas "accomplished, for the first time, that longdesired objective byproperly treating the textile materials with 'the aboveacrOIeimf-Ormaldehyde condensation produot. Materials and garments sotreated will withstand commercial launderings for the normal lifethereof'withoutlosing the crease-resistant characteristics. Furthermore,they will not retain the chlorine which would be 2,771,337 Patented Nov.20, 1956 acid which deteriorates the cellulose and ruins the strength ofthe goods.

We are aware that formaldehyde and compounds which release formaldehydehave been utilized for producing wrinkle resistance and dimensionalstability in cellulosic textile fabrics; however, these formaldehydecompounds have proven unsatisfactory because they tender textile fabricsexcessively. This tenderizing is so pronounced that reaction offormaldehyde with cellulose suflicient to produce a satisfactory degreeof crease resistance in the fabric will cause a loss in strength whichwill destroy the utility of the fabric. In contrast thereto, fabricstreated in accordance with the present invention show little decrease intear strength, tensile strength, or abrasion resistance and, in someinstances, each of these strength properties has been improved by thetreatment and, at the same time, an increase in crease resistance hasbeen noted.

Completely white fabrics may be treated according to this processwithout the yellowing which has been present in fabricstreated withprior art processes. Strong alkali is the known culprit which causesyellowing of fabrics treated with such materials as acetone-formaldehydecondensation products. Commercial chlorine containing bleaching agentsare known to be equally guilty of yellowing fabrics-treated withmelamine formaldehyde type thermosetting resins. Theacrolein-formaldehyde condensation product utilized in this processwithstands repeated attacks by either the strong alkali or the chlorinebleach and, no yellowing is noted on even the whitest goods.

The process of preparing the above aerolein-formaldehyde condensationproduct is shown in the following typical but non-limiting examples ofits preparation given for sake of completeness of disclosure of thisapplica tion.

In the above two examples, utilizing four mols of formaldehyde to, onemol of acrolein, the formaldehyde may be divided into two equal partsconsisting of two mols each. One portion is added to the one mol ofacrolein, which has been freshly distilled so as to have it present inunpolymerized, reactive state. This mixture of formaldehyde andacroflein is relatively stable and may he kept overnight at roomtemperature in the dark. To

the other two. molsof formaldehyde are added sufiiretained bycrease-resistant compounds heretofore used.

Chlorine-retention in the goods is a very undesirable property of theprior treating compositions because of this chlorine, upon subsequentsteaming and ironing of the goods, or garment-s, is converted intohydrochloric cient sodium carbonate to bring the pH of the mixture toabout 9, and to this mixture is then added the acroleinformaldehydemixture. The total amount of sodium carbonate in a typicalcase is about1% based on the total weight of the reaction products, and of thisamount about one-half could be added atfirst to the formaldehydesodiumcarbonate mixture, and then the other half added to the completereaction mixture. The amount of catalyst must be reasonably controlledand kept to less 3 than of the entire mixture to prevent the formationof pentaerythritol.

After the exothermic reaction is completed, the reaction mixture may beneutralized with a suitable mineral acid, such as hydrochloric acid orsulfuric acid, and in suflicient amount to lower the pH of the mixtureto about 2 to 2.5. The reaction mixture is now cooled to roomtemperature and is ready for use in treating textiles in accordance withthe present invention.

Where a slower and less exothermic reaction of acrolein and formaldehydeis desired, an organic catalyst of less basicity may be used in theabove-described reactions.

For example, .05 by weight of 1,5 methyl ethyl pyridine may be used as acatalyst in accordance with the above examples. In such instances, thepH of the mixture at the beginning of the reaction is about 6.7, butgradually increases until it is slightly above 7, and then appears todrop again at the end of the reaction to about 6.5 so that the finishedproduct requires no neutralization.

The reaction product is not a heat-setting resin as are the prior arttextile treating resins. Even long-continued heating in the presence ofan acid producing catalyst does not cause the reaction product toharden. It is instead a cross-linking reagent in that it cross-links thecellulose molecules together to form a stronger, more rigid system thandoes the unreacted cellulose.

A particularly significant characteristic of the acroleinformaldehydecondensation product is its ability to retain its general reactiveproperties when condensed in the presence of polyhydric alcohols.Products of this type, found particularly advantageous in the treatmentof viscose rayon fabrics, may be made according to the followingexamples:

EXAMPLE C A typical procedure for making an oxidized corn starchmodified acrolein formaldehyde condensation product particularly adaptedfor the treatment of viscose rayon and rayon blend fabrics is carriedout by adding 25 pounds of oxidized corn starch to 475 pounds offormalin (37% formaldehyde) in a first kettle and heating the mixture toabout 160 F. with stirring until it is clear. This requires about fiveminutes, after which the reaction mixture is cooled to below 140 F., atwhich time 300 pounds of finely powdered paraformaldehyde are added withcontinued stirring. Simultaneously, 300 pounds of acrolein are distilledinto 385 pounds of formalin in a second separate kettle to form arelatively stable mixture. In a third kettle 14 pounds of soda ash aremade up to a 20% aqueous solution.

The contents of the second and third kettles are simultaneously added tothe reaction mixture of the first kettle with stirring and externalcooling. The condensation reaction is highly exothermic and theintroduction of soda ash and the acrolein-formaldehyde mixture must becarefully regulated to prevent unreasonably high temperatures andpossibly uncontrollable conditions. The reaction product is cooled toapproximately room temperature and brought to pH-2 with muriatic acid.Triethyl amine is then added with stirring to bring the reaction productto pH-9. The product is now ready for storage in drums and is preferablyaged before it is used in the treatment of textile fabrics.

This reaction product possesses the same general properties as that ofExamples 1 and 2, but appears to have a higher molecular weight which isbeneficial in the treatment of viscose rayon.

EXAMPLE D A plain corn starch modified acrolein-formaldehydecondensation product particularly useful for the treatment of celluloseacetate fabrics may be made by adding 48 pounds of corn starch to afirst kettle containing 1,260 pounds of formalin (37% formaldehyde) andheating the mixture to about F. for about 10 minutes, at which time thereaction mixture becomes a clear liquid. Simultaneously, 300 pounds ofacrolein are distilled into 475 pounds of formalin in a second kettle toform a homogeneous relatively stable mixture. In a third kettle, 35pounds of soda ash are made into an aqueous solutionwith 187 pounds ofwater.

The soda ash solution and the acrolein formaldehyde mixture in thesecond kettlet are added simultaneously to the reaction mixture in thefirst kettle with stirring and external cooling. This reaction is highlyexothermic, and the addition of soda ash and the acrolein-formalinmixture must be carefully regulated to prevent excessive heating and apossibly uncontrolled reaction. The thus formed reaction product iscooled to approximately room temperature, at which time the pH isadjusted to 2 by the addition of muriatic acid. The product is thenpreferably stored in drums for several days at approximately 0 C. beforebeing used for treatment of textiles.

Generally, the beneficial results of the present invention are obtainedby treating fabric with an acid liberating catalyst and a water solublecondensation product of acrolein and formaldehyde condensed in the ratioof approximately one mol of acrolein to one to six mols of formaldehyde,and heating the fabric sufiiciently to efiect drying and to cause theacrolein-formaldehyde condensation product to react with the cellulose.

More specifically, the production of crease resistant textiles whichwill resist laundering under relatively high alkaline conditions of theorder of pH 12 and which will not retain the chlorine encountered incommercial laundry bleaching is accomplished by souring the fabric onceor more to the point that less than .01% residual alkali measured assodium hydroxide is left on the fabric, treating the fabric with an acidliberating catalyst and a watersoluble condensation product of acroleinand formaldehyde condensed in the ratio of approximately one mol ofacrolein to four mols of formaldehyde, drying the thus treated textilefabric, and then heating the dried fabric sufiiciently to cause theacrolein-formaldehyde condensation product to react with the celluloseand impart to the fabric the aforesaid characteristics.

Restated, the procedure for using the above-describedacrolein-formaldehyde condensation product for producing the noveleffects on soured textile materials in accordance with the presentinvention is generally as follows: The acrolein-formaldehyde product isdissolved in water using about 5% to 50% concentration, and a suitableacid forming catalyst is added such as hydrochloric acid, sodium acidsulfate, magnesium chloride, zinc nitrate, stearamido mythyl pyridiniumnitrate and octadecyl oxymethyl pyridinium chloride. The amount of acidcatalyst used will vary with the type of catalyst, temperature anddegree of crease-resistance required. In general, the amount of catalystmay vary within a range of about 0.1% to 5%. The cloth is treated withthe catalyzed aqueous solution of the above condensation product andthen dried and cured at a temperature of to 190 C., for a period of fromone to eight minutes, depending upon the type and concentration ofcatalyst used.

Fabrics which contain any residual alkali should be acid soured beforethe application of acrolein-formaldehyde condensation product in orderto obtain the best physical properties of the finished fabric. This stepis particularly important in the treatment of viscose and mercerizedcotton, both of which contain some alkali after even the most vigorouswashings. Souring has been effected by treatment with from .1% to 25%,preferably about 25%, of acid with satisfactory results. Sulfur dioxidehas been used to maintain an acid bath for mild acid treatment.Sulfuric, muriatic and phosphoric acid are examples of suitable strongacids. Organic acids such as acetic and formic acid may be used to goodadvantage with some fabrics, as viscose rayon. The acid treatment a ena-r .5 may bepadded on the fabric or applied inra jig, and followed'byarinse to wash out the acid.

Any neutralization of the sodium ions on the fabric appears to besutficient. Should there be no sodium ions on the cellulosic fabric,the-sou'ring step would be unnecessary. Since most fabrics do containsodium ions, it 'hasbeen found desirable to sour-all fabrics which areto be treated in accordance with the present invention. Tests for propersouring may be made bycareful titration to determine the sodiumions-measured as sodium hydroxide. It has been found that fabrics whichhave .1% alkali measured as sodium hydroxide are too alkaline for properuse in the present invention, and that fabrics which have less than .01%alkali measured as sodium hydroxide are sufiicientlyrneutralized.Fabrics having an intermediate amount of alkalimaybe treated inaccordance with the present invention but with less satisfactoryand-less-un'iformresults than those having less .than .01% residualalkali.

The actual padding of the water solution of the acroleinformaldehydecondensation product is generally the same as conventional treatment offabrics with aqueous solutions of resin forming materials. It has beenfound desirable to provide long immersion and as great a time lag aspractical between the padding of the solution and drying of the fabric.This is to permit maximum penetrationof the acrolein formaldehydeproducts and catalysts into. the fabric.

Drying is preferably accomplished as one operation and heating or curingas a separate operation. However, it is within the scope of thisinvention to accomplish drying and curing in a single operation. Bothprocedures have been successfully carriedout on commercial productionequipment.

Various textile. adjuvants maybe used-with the acroleinformaldehydecondensation product in accordance with .this invention to vary the handand other properties of the treated fabric. A few of the suitableadjuvants are: thermoplastics such as 'methacrylates, polyvinylacetates, etc.; softeners falling into the class of aliphatic.quaternary ammonium compounds, as octadecyl oxymethyl triethyl ammoniumchloride; polymeric polyhydric alcohols, as starch, gumgpolyvinylalcoholand hydroxy methyl cellulose.

Illustrative but non-limiting specific examples of the above-describedgeneral procedure and the productsobtained thereby are as follows:

Example 1 In this example, a 100% cotton Oxford shirting having lessthan .01% residual alkali measured as NaOH was treated with a 12%aqueous solution to the above-described acrolein-formaldehydecondensation product of Example A, and containing%% of magnesiumchloride catalyst. The pick-up or absorption by the cloth of thisaqueous solution was 75%, the solution being applied to the cloth bypadding. Following this padding or impregnating of the cloth with thesolution, the cloth was substantially completely dried, and then heatedin an oven for approximately 170 C. This heat treatment causes theacrolein formaldehyde condensation product, under the influence of theacid producing magnesiumchloride catalyst, to react with the celluloseof the fabric and thereby produce a fabric having resistance to thealkalinity conditions characteristic of commercial laundering andwithout absorption of chlorine commonly used in commercial laundering.

Example 2 .In this example, cotton Oxford shirting which had been souredwith 25% H2804 was treated with a 12% aqueous solution of theacrolein-formaldehyde condensation product as describedin'Examplelabove, except for substitution ofthe magnesium chloride catalyst by 1%of vstearamido methyl pyridinium nitrate (or octadecyl oxymethylpyridinium chloride). The impregnated cloth was.dried as in .Examplefland then heated to a tempcrature of C. for eight minutes to produce afabric having the characteristics described in Example 1. For this lastheating step, the temperature and times may be varied as follows: 70C.-four minutes; C.two minutes; C.one' minute.

Example 3 In this example, the same type of cotton Oxford shirting wastreated with a 10% aqueous solution of the acrolein-formaldehydecondensation product of Example B and 0.5% sodium bisulfate catalyst,following which the impregnated cloth was dried as before and the driedcloth then heated for about seven minutes at 310 F.

Example 4 In this example, mercerized white cotton shirting material wasfirst soured with .25 .HCl and then treated the same as in Example 1above and, in addition, a small amount, i. e., 12 grams for each 250lbs. of the aqueous solution, of Indanthrene Blue R. P. Z. A. was usedfor effecting a permanent whitening of the cloth.

Example 5 A 100% viscose rayon gabardine fabric averaging about 2.10yards per pound, which had been previously dyed with a vat color, wasfirst soured by rinsing 320 yards of the fabric in a' conventional beckcontaining 600 gallons .of a .25% acetic acid. The fabric was agitatedfor one-half hour in the heck, after which the acetic solution wasdrained and the cycle was repeated with another 600 gallons of .25acetic acid. The thus soured fabric was extracted and loop dried. Thesoured and dried fabric was impregnated by padding with a solutioncontaining the following:

15% of the acrolein-formaldehyde condensation product made according toExample C and aged for 22 days at room temperature /s% calcium chloride(anhydrous) 2 /2% oxidized corn starch 1% octadecyl oxymethyl triethylammonium chloride The padding equipment was conventional and in thisexample the squeeze rolls were set at nine-tons pressure to permit apick-up of about 70%. The impregnated fabric was forthwith dried on aclip tenter frame at about 285 F. at a speed calculated to leave about6% moisture in the fabric. The fabric was then cured in a tight strandcurer for about 70 seconds at 375 F. The cured fabric was beck washedwith IgeponT and soda ash, after which it was extracted, loop dried, andframed on a pin tenter.

A separate'piece of the same viscose gabardine fabric, hereinafterreferred to as a water blank, was treated in an identical manner exceptthat it was not padded with the acrolein-formaldehyde fabric formulagiven above. The water blank and the treated fabric were kept understandard conditions for three days, after which they were tested withthe following results:

A 100% cellulose acetate fabric of plain weave running about two yardsper pound was desized and soured in an 80 gallon beck containing 600pounds of water to which sulphur dioxide had been added to the extentthat a pH of 2.65 was obtained. The fabric was agitated for one hour,and the sulphur dioxide solution was then dumped. The beck was refilledwith water, sulphur dioxide was added to bring the pH to two, afterwhich the fabric was again agitated for one hour. The fabric was thenextracted and loop dried. The thus soured and dried fabric wasimpregnated by conventional padding with the following solution:

15% of the acrolein-formaldehyde condensation product prepared accordingto Example D and stored for seven days at C.

1% stearamido methyl pyridinium nitrate 1% methyl methacrylate (35%solids) The padding operation was conventional with about 9- tonspressure on the squeeze roll to permit a pick-up of about 50% based onthe weight of the fabric. The pretreated fabric was forthwith dried in aclip tenter frame at about 230 F., the speed being so adjusted as tobring out the fabric in a slightly moist condition. The fabric was thencured in a loop drier for five minutes at 280 F., after which it wasbeck washed, loop dried, and framed on a pin tenter. Two pieces of thesame cellulose acetate fabric, hereinafter referred to as water blanks,were treated in the same manner except that neither were impregnatedwith the above-described acrolein-formaldehyde fabric treating formula,and one was not soured with the sulphur dioxide solutions.

Example 7 The same cellulose acetate fabric used in Example 6 8 thenpadded with an aqueous solution containing'the following:

15% of the acrolein-formaldehyde condensation product made according toExample C anhydrous calcium chloride octadecyl oxymethyl triethylammonium chloride 1% oxidized corn starch The padding was arranged sothat the fabric picked up about 70% of its own weight of the abovesolution. The wet fabric was run directly into a clip tenter where itwas dried and was then cured on a loop drier for 6 minutes and secondsat 310 F.

Example 9 A 100% viscose rayon yarn dyed plaid averaging about 4 /2yards per pound was first soured by the procedure of Example 8, and thenpadded with about 70% of its weight of a water solution of thefollowing:

15 of the acrolein-formaldehyde condensation product made according toExample C A anhydrous calcium chloride 3.2% oxidized corn starch Thefabric was then dried on a clip tenter and cured for 1 minute and 30seconds at 355 F. in a tight strand curer.

Physical tests of the thus treated fabrics are listed below incomparison with control fabrics heretofore referred to as water blanks:

1 Denotes a gain 1 COO-T491 was soured and treated according to theprocedure of Example 6 with the following formula:

15% of the acrolein-formaldehyde condensation product prepared accordingto Example D and stored for seven days at 0 C.

/s stearamido methyl pyridinium nitrate The fabrics treated inaccordance with Examples 11 and 12 were tested after being held atstandard conditions for three days with the following results:

A 100% viscose rayon gabardine averaging about 2.0 yards to the poundwas first soured with .25 acetic acid in three separate becks for 10minutes each, dried, and

IO amazon (a) cotton wash.

The present invention has been described with particular reference tothe treatment of cellulose in fabric form. However, it is within thescope of the invention to treat all cellulosic textile materials toproduce crosslinking. In other words, the acrolein-formaldehydecondensation products of the present invention may be used to treattextile fabrics, threads, yarns, filaments, fibers, or bulk cellulose.Other permissible modifications and changes in the above-describedprocess and product are indicated in the appended claims.

We claim:

1. A process of producing dimensionally stable, creaseresistantcellulose textile fabric that will resist laundering under relativelyhigh alkaline conditions of the order of pH 12 and that will not retainthe chlorine encountered in commercial laundry bleaching, comprisingimpregating substantially alkali-free cellulose fabric with an aqueoussolution containing from about .l% to 5% of acidic catalyst and fromabout 5% to 50% of an aqueous solution of a water-soluble condensationproduct of acrolein and formaldehyde condensed in the presence of asmall percentage less than 5% of a basic catalyst, said reactants beingin the ratio of approximately one mol of acrolein to four mols offormaldehyde, drying said thus impregnated textile fabric, and thenheating said dried fabric sufliciently to cause theacrolein-formaldehyde condensation product to react with the celluloseand impart to said fabric the aforesaid characteristics.

2. A process of imparting crease-resistance and dimensional stability tocellulose fabric that will withstand commercial laundering conditions ofpH 12 and use of chlorine bleaches for whitening of said fabric, withoutloss of the crease-resistance characteristic and without retention ofthe chlorine, comprising impregnating substantially alkali-freecellulose fabric with an aqueous solution containing from about to 50%of an aqueous solution of a water-soluble condensation product ofacrolein and formaldehyde in which the acrolein is condensed with theformaldehyde in the presence of a small percentage less than 5% of abasic catalyst, said reactants being in the ratio of one mol of acroleinto one to six mols of formaldehyde, the condensation product beingapplied to said fabric in the presence of from about .l% to 5% based onthe weight of the solution of an acidic catalyst, and heating saidtreated fabric to effect drying and reaction of the condensation productwith the cellulose of said fabric.

3. A process of producing crease-resistant cellulose fabric as definedin claim 2 in which the acidic catalyst is magnesium chloride.

4. A process of imparting crease-resistance and dimensional stability tocellulose fabric that will Withstand commercial laundering conditions ofpH 12 and use of chlorine bleaches for whitening of said fabric, Withoutloss of the crease-resistance characteristic and without retention ofthe chlorine, comprising souring said fabric, impregnating saidcellulose fabric with an aqueous solution containing from about 5% to50% of an aqueous solution of a water-soluble condensation product ofacrolein and formaldehyde in which the acrolein is condensed with theformaldehyde in the presence of a small percentage less than 5% of abasic catalyst, said reactants being in the ratio of one mol of acroleinto one to six mols of formaldehyde, the condensation product beingapplied to said fabric in the presence of from about .1% to 5% based onthe Weight of the solution of an acidic catalyst, and heating saidtreated fabric to effect drying and reaction of the condensation productwith the cellulose of said fabric.

5. A process of imparting crease-resistance and dimensional stability tocellulose fabric that will Withstand commercial laundering conditions ofpH 12 and use of chlorine bleaches for whitening of said fabric, withoutloss of the crease-resistance characteristic and without retention ofthe chlorine, comprising impregnating substantially alkali-freecellulose fabric with an aqueous solution containing from about 5% to50% of an aqueous solution of a water-soluble material comprising thereaction product of about 1 to by weight of a starch, one mol ofacrolein, and from about one to six mols of formaldehyde condensed inthe presence of a small amount less than 5% of a basic catalyst, saidreaction product being applied to said fabric in the presence of fromabout .1% to 5% based on the total Weight of the solution of an acidiccatalyst, and heating said impregnated fabric to elTect drying andreaction of the condensation product with the cellulose of said fabric.

6. A process of imparting crease-resistance and dimensional stability tocellulose fabric that will withstand commercial laundering conditions ofpH 12 and use of chlorine bleaches for whitening of said fabric, withoutloss of the crease-resistance characteristic and without retention ofthe chlorine, comprising souring said fabric to the extent that lessthan 01% residual alkali measured as sodium hydroxide remains thereon,impregnating said cellulose fabric with an aqueous solution containingfrom about 5% to 50% of an aqueous solution of a water-soluble materialcomprising the reaction product of about 1 to 10% by weight of a starch,one mol of acrolein, and from about one to six mols of formaldehydecondensed in the presence of a small amount less than 5% of a basiccatalyst, the reaction product being applied to said fabric in thepresence of from about .1% to 5% based on the total weight of thesolution of an acidic catalyst and heating said impregnated fabric toeffect drying and reaction of the condensation product with thecellulose of said fabric.

7. A water-soluble reaction product of about 1 to 10% by weight of astarch, one mol of acrolein, and from about one to six mols offormaldehyde condensed in the presence of a small percentage less than5% of a basic catalyst.

8. A process of producing water-soluble textile treating materialscomprising condensing about 1 to 10% by Weight of a starch, one mol ofacrolein, and from about one to six mols of formaldehyde in the presenceof a small percentage less than 5% of a basic catalyst.

9. A dimensionally stable crease-resistant cellulose textile fabricwhich will withstand commercial alkalinity and bleaching conditionswithout loss of crease-resistance and without chlorine retention, saidfabric being produced by the process set forth in claim 2.

10. A dimensionally stable crease-resistant cellulose fabric which willwithstand commercial alkalinity and bleaching conditions Without loss ofcrease-resistance and without chlorine retention, said fabric beingproduced by the process set forth in claim 5.

11. A process of cross-linking cellulose which comprises impregnatingsubstantially alkali-free cellulose with an aqueous solution containingfrom about 5% to 50% of a water-soluble reactive chemical which is thecondensation product of one mol of acrolein and from about one to sixmols of formaldehyde condensed in the presence of a small percentageless than 5% of a basic catalyst, said solution also containing fromabout .1% to 5% of an acidic catalyst, and heating the thus impregnatedcellulose at a time and temperature suflicient to dry it and to causereaction between said cellulose and said chemical.

References Cited in the file of this patent UNITED STATES PATENTS2,441,859 Weisberg May 18, 1948 2,486,399 Gagarine Nov. 1, 19492,569,932 Izzard Oct. 2, 1951 2,657,192 Miller et al. Oct. 27, 19532,696,477 Gagarine et al. Dec. 7, 1954 FOREIGN PATENTS 349,556 GreatBritain May 28, 1931 OTHER REFERENCES Chem. Abstracts, vol. 24, 1930,pages 5515, 5516, Hanyu et al., Study of the acrolein resins.

7. A WATER-SOLUBLE REACTION PRODUCT OF ABOUT 1 TO 10% BY WEIGHT OF ASTARCH, ONE MOL OF ACROLEIN, AND FROM ABOUT ONE TO SIX MOLS OFFORMALDEHYDE CONDENSED IN THE PRESENCE OF A SMALL PERCENTAGE LESS THAN5% OF A BASIC CATALYST.
 11. A PROCESS OF CROSS-LINKING CELLULOSE WHICHCOMPRISES IMPREGNATING SUBSTANTIALLY ALKALI-FREE CELLULOSE WITH ANAQUEOUS SOLUTION CONTAINING FROM ABOUT 5% TO 50% OF A WATER-SOLUBLEREACTIVE CHEMICAL WHICH IS THE CONDENSATION PRODUCT OF ONE MOL OFACROLEIN AND FROM ABOUT ONE TO SIX MOLS OF FORMALDEHYDE CONDENSED IN THEPRESENCE OF A SMALL PERCENTAGE LESS THAN 5% OF A BASIC CATALYST, SAIDSOLUTION ALSO CONTAINING FROM ABOUT 1% TO 5% OF AN ACIDIC CATALYST, ANDHEATING THE THUS IMPREGNATED CELLULOSE AT A TIME AND TEMPERATURESUFFICIENT TO DRY IT AND TO CAUSE REACTION BETWEEN SAID CELLULOSE ANDSAID CHEMICAL.